Fix the virtual table IN optimizer so that it work even if the virtual table
implementation leaves the sqlite3_index_info.aConstraintUsage[].omit flag
clear for an equality constraint that it intends to use.

Fix the virtual table IN optimizer so that it work even if the virtual table
implementation leaves the sqlite3_index_info.aConstraintUsage[].omit flag
clear for an equality constraint that it intends to use.
(check-in: d6e045f8 user: drh tags: vtab-IN-opt)

Table *pTab = pSrc->pTab;
sqlite3_index_info *pIdxInfo;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int i, j;
int nOrderBy;
double rCost;
/* Make sure wsFlags is initialized to some sane value. Otherwise, if the
** malloc in allocateIndexInfo() fails and this function returns leaving
** wsFlags in an uninitialized state, the caller may behave unpredictably.
*/
memset(&p->cost, 0, sizeof(p->cost));
................................................................................
/* The module name must be defined. Also, by this point there must
** be a pointer to an sqlite3_vtab structure. Otherwise
** sqlite3ViewGetColumnNames() would have picked up the error.
*/
assert( pTab->azModuleArg && pTab->azModuleArg[0] );
assert( sqlite3GetVTable(pParse->db, pTab) );
/* Set the aConstraint[].usable fields and initialize all
** output variables to zero.
**
** aConstraint[].usable is true for constraints where the right-hand
** side contains only references to tables to the left of the current
** table. In other words, if the constraint is of the form:
**
** column = expr
**
** and we are evaluating a join, then the constraint on column is
** only valid if all tables referenced in expr occur to the left
** of the table containing column.
**
** The aConstraints[] array contains entries for all constraints
** on the current table. That way we only have to compute it once
** even though we might try to pick the best index multiple times.
** For each attempt at picking an index, the order of tables in the
** join might be different so we have to recompute the usable flag
** each time.
*/
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
pUsage = pIdxInfo->aConstraintUsage;
for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
j = pIdxCons->iTermOffset;
pTerm = &pWC->a[j];
pIdxCons->usable = (pTerm->prereqRight&p->notReady) ? 0 : 1;
}
memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
if( pIdxInfo->needToFreeIdxStr ){
sqlite3_free(pIdxInfo->idxStr);
}
pIdxInfo->idxStr = 0;
pIdxInfo->idxNum = 0;
pIdxInfo->needToFreeIdxStr = 0;
pIdxInfo->orderByConsumed = 0;
/* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
nOrderBy = pIdxInfo->nOrderBy;
if( !p->pOrderBy ){
pIdxInfo->nOrderBy = 0;
}
if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
return;
}
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++){
if( pUsage[i].argvIndex>0 ){
p->cost.used |= pWC->a[pIdxCons[i].iTermOffset].prereqRight;
}
}
/* If there is an ORDER BY clause, and the selected virtual table index
** does not satisfy it, increase the cost of the scan accordingly. This
** matches the processing for non-virtual tables in bestBtreeIndex().
*/
rCost = pIdxInfo->estimatedCost;
if( p->pOrderBy && pIdxInfo->orderByConsumed==0 ){
rCost += estLog(rCost)*rCost;

Table *pTab = pSrc->pTab;
sqlite3_index_info *pIdxInfo;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int i, j;
int nOrderBy;
int bAllowIN; /* Allow IN optimizations */
double rCost;
/* Make sure wsFlags is initialized to some sane value. Otherwise, if the
** malloc in allocateIndexInfo() fails and this function returns leaving
** wsFlags in an uninitialized state, the caller may behave unpredictably.
*/
memset(&p->cost, 0, sizeof(p->cost));
................................................................................
/* The module name must be defined. Also, by this point there must
** be a pointer to an sqlite3_vtab structure. Otherwise
** sqlite3ViewGetColumnNames() would have picked up the error.
*/
assert( pTab->azModuleArg && pTab->azModuleArg[0] );
assert( sqlite3GetVTable(pParse->db, pTab) );
/* Try once or twice. On the first attempt, allow IN optimizations. ** If an IN optimization is accepted, but does not set the ** pInfo->aConstrainUsage.omit flag, then it will not work (because it ** will allow duplicate rows in the result set) so try again with ** IN optimizations disabled. */ for(bAllowIN=1; bAllowIN>=0; bAllowIN--){ /* Set the aConstraint[].usable fields and initialize all
** output variables to zero.
**
** aConstraint[].usable is true for constraints where the right-hand
** side contains only references to tables to the left of the current
** table. In other words, if the constraint is of the form:
**
** column = expr
**
** and we are evaluating a join, then the constraint on column is
** only valid if all tables referenced in expr occur to the left
** of the table containing column.
**
** The aConstraints[] array contains entries for all constraints
** on the current table. That way we only have to compute it once
** even though we might try to pick the best index multiple times.
** For each attempt at picking an index, the order of tables in the
** join might be different so we have to recompute the usable flag
** each time.
*/
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
pUsage = pIdxInfo->aConstraintUsage;
for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
j = pIdxCons->iTermOffset;
pTerm = &pWC->a[j];
if( (pTerm->prereqRight&p->notReady)==0 && (bAllowIN || pTerm->eOperator!=WO_IN) ){ pIdxCons->usable = 1; }else{ pIdxCons->usable = 0; }
} memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
if( pIdxInfo->needToFreeIdxStr ){
sqlite3_free(pIdxInfo->idxStr);
}
pIdxInfo->idxStr = 0;
pIdxInfo->idxNum = 0;
pIdxInfo->needToFreeIdxStr = 0;
pIdxInfo->orderByConsumed = 0;
/* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
nOrderBy = pIdxInfo->nOrderBy;
if( !p->pOrderBy ){
pIdxInfo->nOrderBy = 0;
}
if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
return;
}
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
if( pUsage[i].argvIndex>0 ){
j = pIdxCons->iTermOffset; pTerm = &pWC->a[j]; p->cost.used |= pTerm->prereqRight;
if( pTerm->eOperator==WO_IN && pUsage[i].omit==0 ){ /* Do not attempt to use an IN constraint if the virtual table ** says that the equivalent EQ constraint cannot be safely omitted. ** If we do attempt to use such a constraint, some rows might be ** repeated in the output. */ break; }
}
} if( i>=pIdxInfo->nConstraint ) break; }
/* If there is an ORDER BY clause, and the selected virtual table index
** does not satisfy it, increase the cost of the scan accordingly. This
** matches the processing for non-virtual tables in bestBtreeIndex().
*/
rCost = pIdxInfo->estimatedCost;
if( p->pOrderBy && pIdxInfo->orderByConsumed==0 ){
rCost += estLog(rCost)*rCost;

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